I recently acquired a D7000 with the goal of using it occasionally for video. The results were somewhat spotty, and they keep going in and out of focus. I read in another forum that it is preferable to use MF lenses as opposed to AF. What is the reason for this? How does the camera retain focus with a MF lens when the subject is moving in a dynamic way?

What sort of settings are recommended in order to get some good quality? (doesn't have to be Oscar level photography

P.S. I have two MF lenses; 28mm and 50mm. AF lenses include 24-120VR, 80-200, 70-300VR.

Manual focus lenses have a bigger focus throw than modern lenses, which makes minor focus adjustments a lot easier. You should also stay in mf all the time for video, the liveview focussing in modern camera's just isn't good. Settings: 1080p (obviously), then adjust sharpness to 0 (all left), contrast down 2 notches, same with saturation. (to get maximum latitude in post) It is near impossible to focus with these settings, so you have to make a high contrast preset and a flat one(this one), like this, you can switch before filming to MF. Then noise reduction off (if you do thid in podt you will get the best results). Never use it above iso 1600 if you want to keep good looking images (unless you have great noise reduction sofftware). Overexpose everything by about 0.7. Use Manual exposure, shutterspeed always at 1/50 if you shoot 24p (most filmic) or 1/60 for 30p. Shoot as much as you can at iso 100, because photo's and video are completely different, D7000 pics look amazing at iso 1600, but video doesn't... If you wan't to shoot without editing: don't change contrast and saturation and set noise reduction to high (won't be as sharp, but will at least have minimal noise), keep other settings. Maybe use S if you don't want to use M for exposure (can be hard and taking a picture is VERY helpfull for checking exposure.